1. Field of the Invention
The present invention relates to hydrostatic seals used between a rotating shaft and a housing.
2. Description of the Related Art
Conventional balanced or pusher-type contacting seals have been used to minimize leakage between a rotating or reciprocating shaft and a housing. However, friction and associated heat production can be significant and in some applications lead to failure of the rubbing elements. As a result it is difficult to predict the performance of such seals.
Hydrostatic and hydrodynamic film riding seals subsequently were developed in order to minimize friction and wear and to allow for more accurate performance prediction. In known hydrostatic seals, a film of fluid between spaced sealing faces replaces conventional contacting sealing elements such as carbon/ metallic rings. Such fluid forming the film is known as an "active" fluid. These seals have proven superior to contacting seals with respect to friction and wear. However, they are subject to leakage problems.
With known hydrostatic seals, either machine fluid leaks out of the housing or active fluid between the spaced sealing faces leaks into the housing. In some applications, when machine fluid from the housing leaks out through the hydrostatic seal, dirt in the machine fluid causes excessive wear to the faces of the seal. This problem becomes especially serious when the machine fluid is a poor lubricant such as FREON.RTM.. Further, excessive leakage of machine fluid from the housing through the seal necessitates frequent replenishing of the machine fluid in the housing and other associated costly maintenance.
In some applications, when active fluid leaks into the housing fluid through a hydrostatic seal, it may be necessary to limit the active fluid to the same substance as the machine fluid. Further, leakage of the active fluid into the housing necessitates frequent replenishing of the active fluid, thus increasing maintenance costs. In other applications, additional problems arise as a result of the leakage of machine or active fluid past the hydrostatic seal.
Accordingly, it is an object of the invention to provide a hydrostatic seal that effectively seals a shaft in a housing against leakage of the machine fluid between the faces of the hydrostatic seal.
It is also an object of the present invention to provide a hydrostatic seal in which active fluid between opposed sealing faces does not leak into the housing.
It is a further object of the invention to provide a hydrostatic seal in which no active fluid or machine fluid leaks out of the seal on the ambient side of the seal.
It is another object of the invention to provide a hydrostatic seal which relies purely on hydrostatic effect of an active fluid and is substantially independent of the dynamic conditions of the sealed system.
It is another object of the present invention to provide a hydrostatic seal that prevents leakage through the seal even when the active fluid has a low viscosity or when the speed of shaft rotation is low.
Similar disadvantages are present with known hydrostatic bearings and accordingly, it is an object of the present invention to provide a hydrostatic bearing in which these disadvantages are overcome.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.